> top > docs > PubMed:2466564 > annotations

PubMed:2466564 JSONTXT

Annnotations TAB JSON ListView MergeView

sentences

Id Subject Object Predicate Lexical cue
TextSentencer_T1 0-119 Sentence denotes Essential histidine residues in dextransucrase: chemical modification by diethyl pyrocarbonate and dye photo-oxidation.
TextSentencer_T2 120-376 Sentence denotes Treatment of Leuconostoc mesenteroides B-512F dextransucrase with diethyl pyrocarbonate (DEP) at pH 6.0 and 25 degrees or photo-oxidation in the presence of Rose Bengal or Methylene Blue at pH 6.0 and 25 degrees, caused a rapid decrease of enzyme activity.
TextSentencer_T3 377-441 Sentence denotes Both types of inactivation followed pseudo-first-order kinetics.
TextSentencer_T4 442-571 Sentence denotes Enzyme partially inactivated by DEP could be completely reactivated by treatment with 100 mM hydroxylamine at pH 7 and 4 degrees.
TextSentencer_T5 572-645 Sentence denotes The presence of dextran partially protected the enzyme from inactivation.
TextSentencer_T6 646-725 Sentence denotes At pH 7 or below, DEP is relatively specific for the modification of histidine.
TextSentencer_T7 726-853 Sentence denotes DEP-modified enzyme showed an increased absorbance at 240 nm, indicating the presence of (ethoxyformyl)ated histidine residues.
TextSentencer_T8 854-1060 Sentence denotes DEP modification of the sulfhydryl group of cysteine and of the phenolic group of tyrosine was ruled out by showing that native and DEP-modified enzyme had the same number of sulfhydryl and phenolic groups.
TextSentencer_T9 1061-1243 Sentence denotes DEP modification of the epsilon-amino group of lysine was ruled out by reaction at pH 6 and reactivation with hydroxylamine, which has no effect on DEP-modified epsilon-amino groups.
TextSentencer_T10 1244-1481 Sentence denotes The photo-oxidized enzyme showed a characteristic increase in absorbance at 250 nm, also indicating that histidine had been oxidized, and no decrease in the absorbance at 280 nm, indicating that tyrosine and tryptophan were not oxidized.
TextSentencer_T11 1482-1622 Sentence denotes A statistical, kinetic analysis of the data on inactivation by DEP showed that two histidine residues are essential for the enzyme activity.
TextSentencer_T12 1623-1767 Sentence denotes Previously, it was proposed that two nucleophiles at the active site attack bound sucrose, to give two covalent D-glucosyl-enzyme intermediates.
TextSentencer_T13 1768-1908 Sentence denotes We now propose that in addition, two imidazolium groups of histidine at the active site donate protons to the leaving, D-fructosyl moieties.
TextSentencer_T14 1909-2115 Sentence denotes The resulting imidazole groups then facilitate the formation of the alpha-(1----6)-glycosidic linkage by abstracting protons from the C-6-OH groups, and become reprotonated for the next series of reactions.
T1 0-119 Sentence denotes Essential histidine residues in dextransucrase: chemical modification by diethyl pyrocarbonate and dye photo-oxidation.
T2 120-376 Sentence denotes Treatment of Leuconostoc mesenteroides B-512F dextransucrase with diethyl pyrocarbonate (DEP) at pH 6.0 and 25 degrees or photo-oxidation in the presence of Rose Bengal or Methylene Blue at pH 6.0 and 25 degrees, caused a rapid decrease of enzyme activity.
T3 377-441 Sentence denotes Both types of inactivation followed pseudo-first-order kinetics.
T4 442-571 Sentence denotes Enzyme partially inactivated by DEP could be completely reactivated by treatment with 100 mM hydroxylamine at pH 7 and 4 degrees.
T5 572-645 Sentence denotes The presence of dextran partially protected the enzyme from inactivation.
T6 646-725 Sentence denotes At pH 7 or below, DEP is relatively specific for the modification of histidine.
T7 726-853 Sentence denotes DEP-modified enzyme showed an increased absorbance at 240 nm, indicating the presence of (ethoxyformyl)ated histidine residues.
T8 854-1060 Sentence denotes DEP modification of the sulfhydryl group of cysteine and of the phenolic group of tyrosine was ruled out by showing that native and DEP-modified enzyme had the same number of sulfhydryl and phenolic groups.
T9 1061-1243 Sentence denotes DEP modification of the epsilon-amino group of lysine was ruled out by reaction at pH 6 and reactivation with hydroxylamine, which has no effect on DEP-modified epsilon-amino groups.
T10 1244-1481 Sentence denotes The photo-oxidized enzyme showed a characteristic increase in absorbance at 250 nm, also indicating that histidine had been oxidized, and no decrease in the absorbance at 280 nm, indicating that tyrosine and tryptophan were not oxidized.
T11 1482-1622 Sentence denotes A statistical, kinetic analysis of the data on inactivation by DEP showed that two histidine residues are essential for the enzyme activity.
T12 1623-1767 Sentence denotes Previously, it was proposed that two nucleophiles at the active site attack bound sucrose, to give two covalent D-glucosyl-enzyme intermediates.
T13 1768-1908 Sentence denotes We now propose that in addition, two imidazolium groups of histidine at the active site donate protons to the leaving, D-fructosyl moieties.
T14 1909-2115 Sentence denotes The resulting imidazole groups then facilitate the formation of the alpha-(1----6)-glycosidic linkage by abstracting protons from the C-6-OH groups, and become reprotonated for the next series of reactions.

NCBITAXON

Id Subject Object Predicate Lexical cue db_id
T1 133-158 OrganismTaxon denotes Leuconostoc mesenteroides 1245

CL-cell

Id Subject Object Predicate Lexical cue cl_id
T1 1085-1092 Cell denotes epsilon http://purl.obolibrary.org/obo/CL:0003025
T2 1222-1229 Cell denotes epsilon http://purl.obolibrary.org/obo/CL:0003025